Tweaking Stem Cell Therapy Use in Horses (AAEP 2012)

Researchers acknowledge that the veterinary community might have started "running with stem cell use before "walking," leaving important questions that need definitive answers before veterinarians can establish and recommend best practices.

Photo: The Horse Staff

Stem cell therapy has evolved rapidly as a treatment approach in veterinary medicine, particularly for addressing musculoskeletal injuries in athletic horses. But researchers are acknowledging that the veterinary community might have started running with the technique before walking, leaving important questions that need definitive answers before veterinarians can establish and recommend best practices. A Louisiana State University research team recently evaluated the use of different stem cell types and presented their findings at the 2012 American Associations of Equine Practitioners’ (AAEP) Convention, held Dec. 1-5 in Anaheim, Calif.

“To derive the greatest benefit from stem cell therapy, we need to optimize and describe (stem cells’) behavior in the laboratory,” said Mandi J. Lopez, DVM, MS, PhD, Dip. ACVS, director of the Laboratory for Equine and Comparative Orthopedic Research, in Louisiana State University’s Department of Veterinary Clinical Sciences. “Ultimately, this is necessary for the preclinical studies to confirm safety and efficacy prior to controlled clinical trials.”

In their study, Lopez and colleagues isolated “multipotent stromal cells” from bone marrow and adipose (fat) tissue. Multipotent stromal cells are immature cells found in adult tissues that are thought to maintain normal tissue and respond to injury by maturing into adult cells as needed. In this sense they are a form of stem cells; however, unlike “totipotent” stem cells (that can become any tissue type), multipotent stem cells are generally limited to becoming the type of tissues from which they’re derived. For example, a mesenchymal stem cell can become muscle or bone cell but not a brain cell. In the study by Lopez et al., veterinarians harvested cells from adipose tissue and bone, so these cells were able able to become tissues such as bone, adipose tissue, and cartilage. “The ability to isolate, grow, and selectively increase the number of these cells in the laboratory, as well as their ability to become different cell types, has been confirmed many times,” Lopez explained. “The focus (of research) has now begun to shift toward determining the best ways to use the cells to meet the needs of clinical patients.”

One way to do this is to use patient cells to grow new or “neo” tissues in the laboratory. In theory, the new tissue can then be applied to either treat or replace damaged tissue, similar to a graft.

Lopez and colleagues looked at the ability of multipotent stromal cells from bone and adipose tissue to become bone, adipose, and cartilage cells, and their ability to produce “neotissue” after the scientists loaded these cells onto pieces of collagen, called a scaffold (they did this using a special instrument called a perfusion bioreactor, which Lopez said “moves the cells suspended in fluid through the scaffold … to equally distribute the cells and maximize the number of cells on the collagen”) . The scaffold provides the framework to which the cells adhere and begin to produce tissue.

After loading, the researchers maintained the cells on the scaffolds in growth conditions for seven, 14, and 21 days. Then they evaluated the number of live cells, distribution in the scaffold, gene expression, and neotissue formation.

“The key finding of this study was that adult equine multipotent stem cells, when loaded onto collagen scaffolds, turned into distinct cell types and produced adipose, bone, and cartilage neotissue,” said Lopez.

Further, when the cells were grown under conditions designed to produce a certain tissue type (bone vs. adipose tissue, for example), the bone marrow cells tended to have earlier expression of bone and cartilage genes, while adipose tissue cells had earlier expression of adipose genes. That said, the microscopic structure of the bone, cartilage, and adipose neotissue produced did not differ among cell types under identical growth conditions.

“This may mean that multipotent stromal cells from both types of tissue (bone and adipose) may be used for tissue regeneration under similar laboratory conditions,” noted Lopez.

Additionally, the researchers determined that the perfusion bioreactor provided an efficient and effective way to load the cells onto the scaffold, potentially minimizing the total number of cells scientists need to generate specific neotissue.

She concluded, “These findings support our ongoing efforts to develop equine stem cell tissue regeneration to provide new and improve upon existing treatment options, especially in the area of fracture repair.”

About the Author

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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